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Re: [PATCH 1/2] BZ#13743: PowerPC - Add a new header for platformspecific functions


On Thu, Mar 8, 2012 at 8:52 AM, Thomas Schwinge <thomas@codesourcery.com> wrote:
> On Thu, 8 Mar 2012 06:34:57 -0500, Ulrich Drepper <drepper@gmail.com> wrote:
>> On Wed, Mar 7, 2012 at 09:16, Steven Munroe <munroesj@linux.vnet.ibm.com> wrote:
>> > Now if you think only PowerPC has these issue, consider all the random
>> > attempts to use the rdtsc instruction you might have seen, and how
>> > useful it would be to have one well defined and correct version every
>> > one could use.
>>
>> If this is a fair comparison then it is also clear that this
>> discussion is completely misplaced here. ?Something as trivial as
>> rdtsc should be handled in the same way as said instruction is: in a
>> header in gcc. ?This way you also reach programmers who are not using
>> glibc ?but instead gcc on other platforms.
>>
>> Since this was brought up on the glibc list I have to assume there is
>> more to it. ?And that means your argumentation is deliberately
>> misleading.
>
> I also wondered about these two issues: why is this to be part of the
> sysdeps/unix/sysv/linux/ hierarchy, given there is nothing Linux-specific
> to it (as far as I can tell), and why is this to be in glibc at all,
> given there is nothing libc-specific to it (as far as I can tell)? ?I
> likewise would assume to find such a generic ``ISA helper header'' as
> part of the compiler itself.

The IBM team have not said that it is *not* Linux specific, so we should
ask them.

There may very well be something Linux-specific, for example on HPPA
we have a cr16 that we can use for hp-timing, but it's only usable on
an OS that synchronizes it among all CPUs that are online. While reading
cr16 is easy, the setup is much more difficult and not mandated by any
ISA.

Regarding the GCC vs. GLIBC header split decision, I've summarized my
opinion, and the points made in this conversation so far:

http://sourceware.org/glibc/wiki/PlatformHeaders

Please comment.

Cheers,
Carlos.


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